1. Field of the Invention
This invention relates to a jack for lifting automobiles and other vehicles. More particularly, the invention relates to an improved construction of a jack to reduce distortion or deflection of the components thereof in use.
2. Description of the Related Art
A portable jack is typically stored in a vehicle to enable the driver to lift a portion of the vehicle to effect emergency repairs, such as change a tire.
A popular jack configuration is known as the pantographic jack. Pantographic jacks typically have four arms hinged in a parallelogram at four joints. One joint is located on a base of the jack, another joint is positioned at a load rest vertically above the base. Two other free floating points are located on a horizontal diagonal at opposite corners of the parallelogram formed by the four arms. When the free floating points are joined together in a horizontal plane for example by means of a drive screw, the arms are extended more vertically to thereby lift the load rest with respect to the base and the vehicle part disposed on the load support. Thus the relative position of the free floating joints is controlled by a drive screw or thread shaft which lengths them together. Typically, one of the free floating joints has a threaded annulus or nut which moves axially along the length of the drive screw in response to rotation of the screw. The other free floating point has a bearing in which the screw turns without changing its axial position with respect to that joint.
Modern automobile design has placed an increasing emphasis on efficient use of space. Thus, jack manufacturers have focused attention on reducing the amount of trunk space required for jack storage. Steps have also been taken to simplify the component parts of the jack and reduce the number of component parts to reduce material and assembly costs and to simplify manufacture.
A so-called Half Scissor Jack has been developed and addresses some of the issues noted above. Typically, a Half Scissor Jack consists of a base, a load rest, a base channel, and a lift channel. These components are usually metal stampings with the base component and the lift component being typically "U"-shaped in cross-section.
The inventor has recognized that when such a Half Scissor Jack is used to raise and support a vehicle, the jack can experience a great deal of torsional deflection through the base channel. This creates the potential for an unstable condition of the jack which can cause the vehicle to fall off the jack.